In many locations, particularly along highways and in certain industrial locations excessive noise occurs which interrupts other uses of the adjacent areas. In prior art structures to address this problem the noise is either reflected by wall surfaces or absorbed by such walls. However the prior art structures are not aesthetically pleasing and frequently have excessive weight and are otherwise difficult to maintain. Structures used in retaining wall installations have been used with some success in attenuating excess noise but such structures inherently failed to absorb adequate amounts of the noise generated due to the angled orientation of the retaining walls and are not free standing adapted to be assembled in open areas such as highway medians and the like. In addition the retaining wall installations require the presence of an earthen embankment against which the retaining wall is placed usually at a substantial angle from the vertical. This structure is not freestanding and cannot fully function as a freestanding noise attenuation barrier. Four or more separate structural elements are typically required for the installation of such retaining wall structures. The retaining wall structures of the prior art have only one exposed face so that it is not suitable for use in a median on a divided highway where both sides are required to have provision for the growth of sound attenuating vegetation.